Cardiac Conduction and APs Flashcards Preview

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Flashcards in Cardiac Conduction and APs Deck (65)
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1
Q

ECG

A

Electrocardiogram

2
Q

What does an ECG measure?

A

Extracellular voltage - difference between regions

3
Q

P wave

A

Atrial depolarization (contraction)

4
Q

At the peak of the P wave, what is contracting?

A

Right atrium

5
Q

When the P wave returns to baseline, what is contracting?

A

BOTH atria

6
Q

PR segment

A

Both atria contracting - baseline

7
Q

QRS

A

Ventricular depolarization (contraction)

8
Q

ST segment

A

Both ventricles contracting - baseline

9
Q

T wave

A

Ventricular repolarization (relaxation)

10
Q

The atrial T wave is hidden behind ____

A

QRS complex

11
Q

R - R interval

A

Periods between ventricular depolarization

- determines heart rate

12
Q

PR interval

A

Contraction and relaxation cycle of atria

13
Q

QT interval

A

Contraction and relaxation cycle of ventricles

14
Q

Bradycardia

A

HR < 60/min

15
Q

Tachycardia

A

HR > 100/min

16
Q

1st degree AV block

A

PR interval > 0.2 ms

17
Q

What is the order that the action potentials spread?

A
SA node
AV node
Bundle of His
R and L bundle branches
Small purkinje fibers
18
Q

Which atrium contracts first?

A

Right

19
Q

Which layer of the heart contracts first?

A

Endocardium

20
Q

Which ventricle contracts first?

A

Right

21
Q

All portions of the action potential pathway can spontaneously generate action potentials under the right circumstances. What is the usual pacemaker of the cycle?

A

SA node

22
Q

All portions of the action potential pathway can spontaneously generate action potentials under the right circumstances. What maintains the correct order?

A

Overdrive suppression

23
Q

Cells with larger diameter have ______ signal propagation

A

FASTER

24
Q

Compared to the AV node, purkinje fibers have ____ signal propagation

A

Faster

25
Q

Which portions of the heart have cardiac FAST action potentials?

A

Atria, ventricles, purkinjes

26
Q

Which portions of the heart have cardiac SLOW action potentials?

A

SA node and AV node

27
Q

Cardiac FAST action potentials involve what phases?

A

0, 1, 2, 3, 4

28
Q

Cardiac SLOW action potentials involved what phases?

A

4, 0, 3

29
Q

Phase 0 of a cardiac FAST action potential

A

INCREASED Na+ conductance into the cell

- (opening of fast na+ channels)

30
Q

Phase 1 of a cardiac FAST action potential

A

CLOSURE of Na+ voltage gated channels

OPENING of transient outward K+ current (Ito)

31
Q

Phase 2 of a cardiac FAST action potential

A

OPENING of voltage gated Ca++ channels
CLOSURE of transient outward K+ current (Ito)
CLOSURE of inward rectifying K+ channels

32
Q

Phase 3 of a cardiac FAST action potential

A

CLOSURE of voltage gated Ca++ channels
OPENING of inward rectifying K+ channels
**OPENING of voltage gated K+ channels (Ikr and Iks)

33
Q

Phase 4 of a cardiac FAST action potential

A

Resting membrane potential due to the Na+/K+ ATPase

34
Q

What enters the cell during phase 0 of a cardiac FAST action potential?

A

Sodium (Na+)

35
Q

What leaves the cell during phase 1 of a cardiac FAST action potential?

A

Potassium (K+)

36
Q

What enters the cell during phase 2 of a cardiac FAST action potential and what remains inside?

A
Calcium enters (Ca+)
Potassium remains inside the cell (K+)
37
Q

What leaves the cell during phase 3 of a cardiac FAST action potential?

A

Potassium (K+)

38
Q

When do the sodium channels open during a FAST action potential?

A

Phase 0

39
Q

When do sodium channels closure during a FAST action potential?

A

Phase 1

40
Q

When does the transient outward K+ current open during a FAST action potential?

A

Phase 1

41
Q

When does the transient outward K+ current close during a FAST action potential?

A

Phase 2

42
Q

When does the Ca+ channels open during a FAST action potential?

A

Phase 2

43
Q

When does the inward rectifying K+ channels close during a FAST action potential?

A

Phase 2

44
Q

When do the inward rectifying and voltage gated K+ channels open during a FAST action potential?

A

Phase 3

45
Q

Long QT syndrome

A

Transition from phase 2 - phase 3 is lengthened

46
Q

What can be influenced with Long QT syndrome?

A

Voltage gated K+ channels (Ikr, Iks)

47
Q

Phase 4 of a cardiac SLOW action potential

A

Slow influx of Na+ due to opening of “funny” voltage gated Na+ channels after repolarization

48
Q

Phase 0 of a cardiac SLOW action potential

A

OPENING of CA++ channels

CLOSURE of inward rectifying K+ channels

49
Q

Phase 3 of a cardiac SLOW action potential

A

CLOSURE of Ca++ channels

OPENING of delayed rectifying K+ channels

50
Q

What causes phase 0 in a cardiac SLOW action potential?

A

Opening of calcium channels!!

not sodium like in fast action potentials

51
Q

Parasympathetic ____ heart rate

A

SLOWS

52
Q

Sympathetic ____ heart rate

A

INCREASES

53
Q

What nerve is the parasympathetic innervation to the heart?

A

Vagus

54
Q

What is the NT for parasympathetic innervation to the heart and what receptor does it bind?

A

Acetylcholine –> muscarinic receptor

55
Q

Does parasympathetic innervation influence contractility?

A

NO

56
Q

What is the adjustment that occurs for parasympathetics to decrease heart rate?

A

Slower entry of sodium during phase 4

57
Q

What is the NT for sympathetic innervation to the heart and what receptor does it bind?

A

Norepinephrine –> beta1 adrenergic receptor

58
Q

Does sympathetic innervation to the heart increase contractility?

A

YES

59
Q

What is the adjustment that occurs for sympathetics to increase heart rate?

A

Faster entry of sodium during phase 4

60
Q

No AP can be generated

A

Absolute refractory period

61
Q

AP can be generated, but will require a larger stimulus

A

Relative refractory period

62
Q

Cell is actually more excitable than normal but AP will be abnormally conducted

A

Supranormal period

63
Q

Hyperkalemia ____ phase 0

A

SLOWS

64
Q

Hyperkalemia ____ phase 3

A

Speeds

65
Q

Hyperkalemia causes the membrane potential to be more?

A

Positive